04:36PM | 07/16/03
Member Since: 07/15/03
1 lifetime posts

Everytime I run my air conditioner there is a very loud rattling noise. I was told by one HVAC tech that if the squirrel cage(blower wheel) and blower motor are replaced the noise will stop. Another HVAC tech said the blower cage needs to be replaced in order to stop the noise. Is there such a thing as a blower cage? Does the blower motor "fit" inside of the squirrel cage (blower wheel)? I need to get this problem fixed asap and I'm unsure who is telling me what the correct "fix" is.

Thanks for your help!!!


05:06PM | 07/16/03
Member Since: 06/06/03
1250 lifetime posts
Greetings Tricia,

I'd reckon the 2 HVAC folks are saying about the same thing. The squirrel cage is a kind of big fan (or blower) and I'd believe it could make noises like you describe if it goes bad. It gets its name 'cause it's shaped kind of like those little wheels that hamsters run around on.

As for the motor being inside the cage, I'm not familiar with all the configurations but it's believable. They're often belt driven with the motor outside the cage. I would wonder if the existing squirrel cage could be lubricated, but these days most of them are "permanently lubricated", meaning that the HVAC folks may be right and they may have to be replaced when they go bad.

Hopefully one of the HVAC gurus will respond, but in the meantime, I'd be tempted to go with the one who'll fix it for less $$$. Good luck!

plumber Tom

06:18PM | 07/16/03
Member Since: 05/10/03
810 lifetime posts
Check the set screw on the blower motor shaft. It's possible the screw loosened up, and the squirrel cage is hitting the housing. You need the long handled Allen keys for this application.


07:48PM | 07/19/03
Some times the bearing in the motor begin to go bad and throw the unit out of balance and cause the noise. It is also possible that one of the 'cups' on the blower wheel has loosened up as well. It sound like they are both on the right track.


02:21PM | 07/20/03
Member Since: 06/09/03
7 lifetime posts
Unless your HVAC guys actually removed the cover of your unit and slid out or dismounted the cage, they probably don't know if the motor and/or cage need replacement.

A cage driven by a belt from a motor outside the cage that has become misaligned or out of balance would probably produce a whirling, scrapping or rubbing noise. A motor with worn bearings, either inside or outside the cage, sounds like just what is is - a noisy motor - you described your noise as a rattle.

So - I'm guessing that your unit is a "direct drive" - that is, the motor is mounted inside the cage. Different brands of motors are mounted to the cage with different sets of brackets - these attached with straps/bolts/nuts that can loosen over time. We have replaced the 1/3 HP motor on our air-handler twice - each time the motors available with the proper HP, speed(s), shaft length & diameter didn't match the last set of brackets and we had to buy new sets and/or improvise.

It is a lot easier for your HVAC guys to bring out a premounted motor in a cage that just slides into your unit and wire in the motor's color-coded 2-speed, 3-speed, single-speed wires than to disassemble it to find the exact cause of your rattle. Depending on his hourly rate and what the problem is, it might be cheaper too because it's faster.

So, if I was your HVAC person and had to give you a quote, I'd probably give you the same answers as they did - most customers just want the #!%$ thing fixed.



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